ewerbeck



April 15 1924.

P. EWERBECK ELECTRIC FURNACE Filed Jung 4, 1921 Sheets-Sheet 1 April 15 1924,

P. EWERBECK ELECTRIC FURNACE Filed June 4. 1921 3 Sheets-Sheet 2 fllarez c a]:

April 15 1924.

P. EWERBECK ELECTRIC FURNACE s Sheets-Sheet 5 Filed June 4, 1921 I :21) ere/5011 1? 11116115601; 27

Patented Apr. 15, 1924.

UNITED STATES 1,490,530 PATENT OFFICE.

PAUL EWERBECK, OF GARMISOH, GERMANY.

ELECTRIC Application filed June 4,

To all whom it may concern:

Be it known that I, PAUL EWERBECK, residing at Garmisch, Bavaria, Germany, have invented certain new and useful Improvements in Electric Furnaces (for which I filed application in Germany on Feb. 21, 1920), of which the following is a specification.

This invention relates to a means of using electricity as a substitute for coal in calcining limestone for the purposeof ex elling the carbonic acid or water containe in it. In accordance with the invention the limestone from the quarry is introduced in a manner hereinafter more fully described into a drum adapted to rotate about a horizontal axis. The electric heating elements employed consist of pieces of carbon, carbon encils, or rods or resistance wires which are eated to incandescence by an electric current and are arranged in straight lines in channels running arallel to the axis of the drum in the mant e or circular wall of the same. If the material of which the resistances are made is'oxidizable the said channels are either made ap roximately devoid of air or they are fill with inert gases. The drum is constructed of non-conducting material such as fire-clay. An importantfeature in the construction of the furnace is an arrangement by which the electrical resistances are prevented from making direct contact with the drum and are enabled to expand freely in the said channels. By this arrangement the stresses and cracks in the drum that would arise if the resistances were firmly fixed in the material of the drum are avoided. The said resistances are connected in groups arranged in parallel connection. The one group receives current through a semi-circular conducting bar embedded in the front end of the drum and to which the current is led through a slip ring. The said current after passing through the said group of resistances flows into a closed ring-shaped conducting bar at the other end of the drum and passes thence into a second group of resistances or heating elements which conduct the current into a secondsemi-circular conducting bar embedded in the front end of the drum, whence it passes through a second slip ring back to the current supply mains. By this arrangement breakdowns due to the rupture or failure of heatin elements or wires are completely avoided, because the failure of a said element will only result in an inappreciable increase of electric tension the escape of heat to the outside is pre- FURNACE.

1921. Serial No. 475,173.

in the other elements so that the calcination of the charge in the furnace may be proceeded with without interruption until the process is finished, whilst if the heating or to resistance wires were connected in series or consisted of a single wire wound in the form of a helix around the mantle of the drum, a single rupture of the wire at any point woul stop the flow of current and put the furnace out of commission, thus giving rise not only to serious breakdowns but also to considerable expense, because if the resistance is wound in the form of a helix the fault could not be repaired by simply puttin in a new wire.

' he arrangement of the furnace should be such that the greatest possible amount of the heat produced is radiated inwards and that 7| vented. This is accomplished by a thick heat retaining mantle or cylinder of Suitable material such as fire-clay. During the process of calcination the drum is kept slowly revolving so that the limestone which has been broken by a crusher into fra cuts of a diameter of a few centimeters 18 continually stirred and all parts of the same are brought into contact with the hot surface of the mantle. In distinction from the limestone furnaces used hitherto, in which a continual flow of cold air through the furnace is provided for, the new furnace is arranged to be kept entirely closed whilst in operation so as to render possible a more complete utilization of the heat developed. As a result of this arrangement the new calcination process enables a by-product which was lost in the old process to be turned to account. This by-product, which is carbonic acid (CO and which escapes into the air in the calcination process employed hitherto, may be drawn off by a pump and utilized as a manure or fertilizer either in a gaseous form for plantations in the neighbourhood of the works, or in a liquid form at any distance from the plant after it has been compressed by a compressor. Practical experiments have shown that the crops obtained may be increased in this way 1% to three fold.

The invention is shown in the drawing in which- Fig. 1 is a vertical longitudinal section through the furnace,

Fig. 2 is a detail section on an enlarged scale of a portion of one end of the furnace showing the slip rings,

Fig. 3 is a cross section on the line C-D of Flg. 1,

Fig. 4 is a cross section on the line E-F of Fig. 1, and Fig. 5 is a detail section on an enlarged scale similar to Fig. 1 showing the circular conducting ring and the heating element.

As the temperature required for expelling the carbonic acid is theoretically 800 Celsius and the carbonic acid to be extracted amounts to about 40% of the raw material treated, considerable pressure is developed. To eliminate danger of damage to the drum due to excessive pressure a pipe a is arranged at one of the ends 8 of the drum 9. This pipe a terminates in a safety valve 10 which allows the superflous air to esca e when the pressure becomes excessive. e carbonic acid produced is drawn off by a pump (not shown) connected to the said pipeo. lVhen the development of carbonic acid begins, which happens when the temperature reaches 800, it is of course necessary to stop the rotation of the furnace. The pressure and temperature in the furnace are indicated by means of a pressure gauge 0 and a thermometer (Z, respectively connected to the pipe a.

To make the working of a furnace profitable it has to be made at least 5 metres long and 1% metres in diameter. Hence, a uniform distribution of the raw material throughout the interior of the furnace at the necessary high temperatures cannot be obtained by manual methods. For this reason a special mechanical contrivance is provided for charging the furnace. This contrivance consistsof a flat truck or a. platform 11 run ning on rolls 11 that travel on rails 12 fixed by means of channel iron girders at opposite sides of the drum. \Vhen the loaded truck is to be introduced into the furnace the latter is turned on its supporting rollers 9 into a position in which the said rails 12 lie side by side in a horizontal plane. After the truck has been pushed in through the'doorway 8, the furnace is turned about its longitudinal axis through 180 so that the material to be calcined, which is evenly distributed over the deck of the truck, drops down onto the lower half of the drum 9. The lateral flanges 14 extending along the sides of the platform or deck of the truck will now have dropped down onto the rails 12 along which the rolls of the truck travelled when the latter was pushed into the furnace. The

truck. with its rolls upward and its flanges.

of the drum, the current is also used for heating the furnace by means of wires or heating elements 18 which are freely suspended in channels 19 in the mantle or wall of the drum. The ends 8 of the drum are of fireproof and electrical non-conducting material and said wires are attached to a conducting rin 20 at oneend of the furnace, as shown in circular conducting bars 21 at the other end of the furnace, as shown in Fig. 3. The current is conducted from the supply mains through brushes 22 and slip rings 23, Fig. 3, to the two semi-circular conducting bars 21 and through the heating elements 18 to the ring 20.

At the conclusion of the calcination process the furnace is reopened and the truck is slipped into the same on its side flanges 14 with its rolls 11 upward. Then the furnace is turned until the rolls 11 of the truck land upon the rails 12 at opposite sides of the furnace. By this operation the finished prodnot in the furnace is caused to fall into the truck, which can now be easily drawn out as it will travel on its rolls.

I claim 1. An electric furnace comprising, a horizontal revolving drum with a cylinder and two ends consisting of a fireproof non-conductor of electricity, channels in the cylinder extending parallel to the axis of revolution of the drum, a conducting ring attached to one end of the furnace, two semi-circular conducting bars attached to the other end of the furnace, sliprings for conducting current to the semi-circular bars, and electrical heating elements extending from the semi-circular bars to the said ring and suspended freely in the said channels.

2. An electric furnace comprising, a horizontal revolving drum with a cylinder and two ends consisting of a fireproof non-conductor of electricity, channels in the cylinder extending parallel to the axis of revolution of the drum, a conducting ring attached to one end of the furnace, two semicircular conducting bars attached to the other end of the furnace, sliprings for conducting current to the semi-circular bars, electrical heating elements extending from the semi-circular bars to the said ring and suspended freely in the said channels, tracks extending along opposite internal sides of the said cylinder in directions parallel to its axis of rotation, a truck, rolls attached to the said truck and adapted to travel on the said tracks when the truck is introduced into the cylinder, and flanges at the sides of the said truck and adapted to slide on, the said tracks when the truck is removed from the said cylinder.

3. An electric furnace comprising, a horizontal revolving drum with a cylinder and two and: consisting of a fireproof non-conigs. 4 and 5, and to two semi-v ductor of electricity, channels in the cylinder extending parallel to the axis of revolution of the drum, a conducting ring attached to one end of the furnace, two semi-circular conducting bars attached to the other end of the furnace, sliprings for conducting current to the semi-circular bars, electrical' heating elements extending from the semicircular bars to the said ring and suspended,

.drum with a cylinder and two ends consisting of a fireproof non-conductor of electricity, channels in the cylinder extending parallel to the axis of revolution of the drum a conducting ring attached to one end of the furnace, two semi-circular conducting bars attached to the other end of the furnace, sliprings for conducting current to the semi-circular bars, electrical heating elements extending from the semi-circular bars to the said ring and suspended freely in the said channels, tracks extending along opposite internal sides of the said cylinder in directions parallel to its axis of rotation a truck, rolls attached to the saidtruck an adapted to travel on the said tracks when the truck is introduced into the cylinder flanges at the sides of the said-truck an adapted to slide on the said tracks when the truck is removed from the said cylinder, a safety valve, a conduit leading from the interior of the cylinder through one of its ends to the said safet valve, and a pum joined to the said con uit. v

In testimony whereofl have signed my name to this specification in the presence of two subscribing witnesses.

PAUL EWERBEGK.

\Vitnesses EDGAR BETHToL'z, LUDwm AMEND. 

